North Korea announced a live-fire drill near its maritime border with South Korea today, prompting Seoul to vow a "strong" response after a similar exercise a month ago triggered an artillery exchange.

South Korean fishing vessels were told to stay away from the area and local officials on the border islands of Yeonpyeong and Baengnyeong said residents were advised to take precautions.

North Korea carried out a similar drill on March 31 during which a number of shells dropped into South Korean waters.